Tension meansuring device



June 10, 1941. LILJA 2,245,039

TENSION MEASURING DEVICE Filed MBICh 15, 1959 INVENTOR Edgar D. LL'ZJ'aBY C PM Gw n 4 ATTORNEYS Patented 1 10, 1941 UNITED STATE PATENT OFFICECompany, of Illinois Application mi. 13, 19:9, Serial SOIaIInS.

The invention relates to devices for measuringthe tension in a travelingstrand and more particularly to devices incorporating electrical meansfor damping out vibrations.

'ihegeneral object is to provide a tension measuring device having amagnetic damping means which is of simple and rugged constructionandcontributes to the accuracy '01 the tension measurement.

Further objects and advantages of the invention will become apparent asthe following description proceeds, taken in connection with the asdrawing. in which Figure 1 is a perspective view of a tension measuringdevice embodying the invention,,the' device being shown as applied to atraveling yarn strand.

'l 'lg. 3 is a plan view of thedevice of Fig. 1 with the cover removed.

3 is a longitudinal vertical sectional view oi the device of Fig. l. thesection being taken along the line 3-3 in Fig. 2.

Fig. 4 is an enlarged detail perspective view of a brake magnet and itsassociated parts inciuded in the device of Fig. 1.

Fig. 5 is an enlarged detail perspective view of an alternative i'orm oibrake magnet which may be substituted for that-oi Fig. 4-

The invention has been exemplified herein as embodied in a portable unitsuitable for measltockiord, 11]., a corporation circular shape fixed ona pivot pin it. (Fig. 3) has pointed ends journaled in bearings it andII respectively fixed in the bottom castheyarnisthreaded uring thetension in a traveling strand oi yarn Aas, for example, in the course ofwinding or unwinding the yarn in various operations in a textile mill.Although this particular embodiment oi the invention has been shown anddescribed herein in some detail ior purposes of iilustration andexplanation, there is no intention to thereby limit the invention tosuch embodimeat. but, on the other hand, the appended claims areintended to cover all modifications and alternative constructionsfalling within the spirit and scope of the invention.

The unit of Fig. 1 has been shown as housed within a sectional casingembodying a shallow cup-shaped bottom section II provided with aremovable cover or top section I i which is screwed to it. To avoidinterference with the action of a magnetic device included in the unitas is hereinafter described, the casing sections il-ll are preferablymade oi non-magnetic material and may be economically molded fromsynthetic The tension measuring mechanism the casing il-llis oi theresistor spring typ and embodies a movable member or rotor ii oi seml-'in strand tension, the spring directio threaded in a frame plate il thehearing I! being held in adjusted position by alock nut ii. The frameplate I (Fig. 2) is screwed to the top of the casing section II. It willthus be seen that the rotor i2 is oscillatable about the axis of the pinii. The are of oscillation is limited, however, by a stop arran ementcomprising an upwardly projecting lug it on the rotor l-I and which isreceived in an arcuate slot it in the irame plate it, the ends of theslot defining limit stops.

The rotor i2 is caused to move about its pivotal axis through an areproportional to the tension in the yarn strand A. For this purpose,through a grid (Fig. 1) formed by a pair of upright posts or guides 2|fixed tothe cover Ii and an intermediate post 2i fast on the rotor i2and projecting through an arcuate slot 2! in the casing cover. Enlargedheads serve to hold the thread on the posts Ill. An arrow 23 molded onthe cover ii indicates the direction of yarn travel. With the yarnstrand A led alongside the posts 2! and around the opposite side of themovable post Ii in the manner shown in Fig. 1, it will be apparent thatan increase in strand tension tends to swing the post 2| and hence therotor i! in a counterclockwise direction (as viewed in Figs. 1 and 2).Such movement is yieldably resisted, however, by a contractile spring llstretched between a pin 25 on the rotor i! and an adjustable arm 29.Consequently, as the tension in the yarn strand A is increased, therotor i2 is swung proportionally further in a counter-clockwisedirection and similarly upon a subsequent decrease 2| returns the rotoring section II and.

in a clockwise n.

A visual indicator arranged to be actuated by the rotor I! has beenshown herein as includin a stationary scale it and a cooperating movablepointer 21. The scale 28 may be suitably graduated as, for example, inounces in accordance with the manner in which the the rotor i2 .varieswith changes in the yamas evidenced by the non-uniiorm character oi thescale. The latter is located beneath a registering slot 2'' in the coverIi which is closed by a glass'fl". The pointer 11 has been shown as anintegral extension on a metal plate 20 fast on the rotor i2 andconstituting. as is hereinafter explained in greater detail, a part ofthe rotor damping mechanism.

tension.

To facilitate adjustment of the spring 23 so as to calibrate theinstrument while minimizing minimum and maximum scale error, theadjustable arm, 29 is pivoted on the lower casing section It and is heldin its adjusted position by a screw 3|]. By changing the position of thearm 2!,the tension in the-spring 23 can, of course, be readily adjusted.With the arrangement shown, when there is no tension on the yarn strandA, the

rotor post 2| is at the left hand extremity of its path of movement andthe pointer 21 is at the right hand end of the scale 26. If tension isapplied to the yarn strand A, the rotor l2 will be pulledcounter-clockwise against the yielding resistance of the spring 24 andthrough a distance dependent upon the yarn tension. Consequently, theposition of the pointer 27 on the scale 23 will at all times indicatethe yarn tension. Furthermore, the yarn strand can travel lengthwisefreely through the grid formed by the posts 20 and 2| so that nointerruption in the yarn movement is occasioned by the measuringoperation.

' It will be apparent that with the arrangement so far described, anysudden jerking or rapid changes in tension will cause the rotor |2 tooscillate and render it diillcult to obtain a satisfactory reading ofthe indicator. This condition of sudden irregularities in tension is onewhich is likely to occur, however, in many instances and particularlywhen a yarn strand is being unwound from a cheese or packageof yarn insuch manner that loops are likely to be thrown oiI. Accordingly, theinvention contemplates the provision of means particularly suited to theconditions encountered in service use of the indicator and operableeffectively to damp the movement of the shiftable indicator element orpointer 21. In the present instance, this means comprises an eddycurrent brake type of damping mechanism which serves to-dainp out moreor lessmomentary fluctuations of indicator movement without impairingthe accuracy or registration of steady state conditions. The dampeneralso functions automatically to vary'the damping action in accordancewith the prevailing tendency of the indicator to vibrate with tensionchanges in the strand.

To provide for structural simplicity and compactness, the dampingmechanism is of special construction andassociated in a novel way withthe other parts of the instrument. Herein, it comprises a permanentmagnet 3| in the form of a loop with its ends spaced apart on one sideof the loop. and forming pole faces disposed in inductive relation withrespect to a member 33 of non-magnetic and conductive material carriedadjacent the faces of the poles 32 and 32 and overlapping the latter.The magnetic circuit between the pole pieces 32 and 32 is completedthrough a keeper or bridge fashioned of magnetic material in the form ofa segmental plate 33 screwed to the cover ll (Fig. 3) and having polepiece projections 33* and 33 (Fig. 4) with faces registering with andopposed to the pole pieces 32* and 32b and lying alongside the inductorplate closely adjacent the latter.

With the arrangement shown in Fig. 4, the major portion of the magneticflux follows the path indicated by the line of arrows 36. In the eventthat the pole piece 32 is a north pole and the pole piece 32 a southpole, the flux passes -from the north pole 32" through the inductor 33and into the opposed pole piece 3l*,.,thence to the other keeper polepiece 35 and back through the inductor 33 to the magnets south polepiece 32 Clockwis motion of the inductor member 33, relative to thisflux, induces-eddy currents in the member which react with the flux andfollow roughly theorbital paths indicated by the lines of arrows 31. Theeddy currents thus set up resist relative motion between the inductormember 33 and the associated magnet structure 1 in a manner wellunderstood in the art so that oscillatory or other transitory movementsof the indicator pointer 21 are damped efl'ectively. The magnitudes ofthe eddy currents will be in proportion to the rapidity of oscillationof the inductor plate so that the degree of damping will increase withan increase in the tendency of the indicator to vibrate.

by and movable with the rotor plate 23. In the .form shown in Figs. 2 to4, the ends 32' and 32 of the magnet which constitute pole pieces arespaced apart circumferentially and are turned outwardly to provide polefaces generally paralleling the plane of the magnet loop. To localizethe flux in the pole pieces and avoid leakage, the ends of the magnetare beveled as indicated at 3|. The magnet loop is fastened by screws 3|in the casing section I! and is offset from the rotor axis so that thelatter is disposed adjacent the side of the loop diametrically oppositefrom the poles preferably within the magnet loop. Preferably, the magnetis composed of a material sold under the trade name of "Alnico whichpossesses high coercive force and may be strongly magnetized.

The inductor member 33 comprises a segmental extension of the rotorplate 23 lying closely In the operation of the device, a travelingstrand, whose tension is to be measured, is slipped into positionbetween the posts 20-2! in the manner of the yarn strand A in Figs. 1and 3 with the direction of strand motion corresponding to the arrow 23.Thereafter, the strand pulls the rotor post 2| to the right orcounter-clockwise against the resistance of spring 24 a distanceproportional to the tension in the strand. Accordingly, a continuousvisual indication of strand tension is afforded by the position of thepointer 2! on the scale 28. Furthermore, the pointer 21 shifts only withchanges in mean or steady state value of the strand tension due to thedamping or stabilizing effect of the eddy current brake so that there isno such substantial oscillation of the pointer as would otherwise resultfrom sudden brief changes in tension. This makes the instrument usablefor such purposes as the measurement of tension of yarn being unwoundfrom a yarn package under conditions where loops are likely to be thrownoil intermittently with consequent abrupt and brief changes in tension.

In Fig. 5, an alternative form of magnet 33 has been illustrated andwhich may be substituted for the magnet 3| of ,Fig. 4. No separatekeeper or bridge such as the part 34 of Fig. 4 is required. Thepermanent magnet 33 is similar to magnet 3| heretofore described in thatit is also of generally loop shaped configuration. It is spiraledsomewhat, however, so that pole piece projections 39 formed on its endsare spaced apart axially of the magnet rather than circumferentially.With such an arrangement. the inductor member 33 may be received in theair gap between the opposed pole pieces 3!. The flux threading theinductor member between these polepieces reacts with the moving inductormember-i to produce eddy currents in the latt r which react with theilux to resist its moveaasaoso ment and accomplish the desired dampingoi the pointer motion in the same general manner as in the arrangementoi Fig. 4.

It will be apparent from the ioregoing that the damping mechanism, beingoi magnetic character, is not influenced by iriction so that themagnitude of the damping action corresponds accurately to the tendencyoi the indicator to vibrate. By employing a ring-shaped magnet andlocating the same as described relative to the pivotal axis oi theindicator member, the magnet may be dimensioned properly whilemaintaining a high degree of compactness in the parts oi the instrument.

I claim as my invention:

1. A device ior measuring traveling strand comprising, in combination, astationary permanent magnet comprising a bar oi permanently magnetizedmaterial iorming a loop having its ends spaced apart circumierentiallyand providing pole iaces spaced circumierentially and iacing laterallyoi the loop, a magnetic bridge disposed alongside said magnet ends andoverlapping but spaced laterally irom said iaces, a non-magnetic andelectrically conductive inductor member pivotally mounted for movementgenerally parallel to the plane oi the loop and longitudinally oi thegap between said bridge and said pole faces with the nu: through saidgap threading said inductor member, whereby the movements oi saidinductor member are damped as a result oi the eddy currents inducedtherein, an indicator arm swingable alongmdle said loop with saidinductor member, means yieldably urging said indicator arm in onedirection, and means including a projection on said inductor memberenSI-Beflble with a traveling strand to cause said arm to be deflected adistance proportional to the tension in the strand said yieldable means.

2.A device ior measuring the tension in a traveling strand comprising,in combination, a

the tension in a stationary permanent magnet in the iorm oi a loop withthe ends disposed adiacent each other and providing pole iaces iaoinglaterally oi the loop, a non-magnetic and electrically conductiveinductor member pivotally mounted for movement generally parallel to theplane oi the loop and edgewise through the path oi flux threading thegap between said pole faces, whereby the movements of said inductormember are damped as a result of the eddy currents induced therein, anindicator arm swingable alongside said loop with said inductor member,means yieldably urging said indicator arm in one direction, and meansincluding a projection on said inductor member engageable with atraveling strand to cause said arm to be deflected a distanceproportional to the tension in the strand opposing said yieldable means.

3. A device ior measuring the tension in a traveling strand comprising,in combination, a stationary permanent magnet in the form oi a loop withthe ends overlapping each other circumierentially and providing poleiaces facing laterally oi the loop in opposed spaced relation, anon-magnetic and electrically conductive inductor member pivotallymounted ior movement generally parallel to the plane oi the loop throughthe gap between said pole faces with the flux through said gap threadingsaid inductor member, whereby the movements oi said inductor member aredamped as a result oi the eddy currents induced therein, an indicatorarm swingable alongside said loop in unison with said inductor member,means yieldably urging said indicator arm in one direction, and meansincluding a projection on said inductor member engageable with atraveling strand to cause said am to be deflected a distance proprtional to the tension in the strand opposing said yieldable EDGAR D.LII-TA.

